The plaintiffs lawyers bringing the shareholder class action suit over the collapse of commodities brokerage Refco Inc. have been receiving assistance from an unlikely source — Refco’s former chief executive officer.

John P. Coffey of Bernstein Litowitz Berger & Grossman and Stuart M. Grant of Grant & Eisenhofer disclosed in a letter Thursday to Southern District of New York Judge Naomi R. Buchwald that they held “several highly productive meetings” with ex-Refco boss Philip R. Bennett, who provided them with a “unique opportunity to debrief a former CEO involved in a massive corporate fraud.”